Hello,
Please feel free to post topics scientific and technological in this forum…been sanctioned from on high.
I’ll do my best to lure people in but going to be busy with work for a few days so please add to the science topics already here and add new ones so I can get my teeth sunk in with the rest of you in a few days.
Thap.
PS: Well better than nothing
No. This is not the “Technology” forum.
http://www3.pak.org/gupshup/smilies/smile.gif
However, go ahead and discuss Science topics here. Lets see.
Pristine,
Is this guessing game for my benefit?
I was just told in my thread in the cafe that S&T related topics are to be moved here.
"Lets see"......doesn't sound very encouraging!!!...
Pull some strings P and get a forum set up.
can u tell us the scientific events that took place between 1901-1905
Well the chemist Linus Pauling and the physicist Werner Heisenberg, were both born in 1901.
It’s not a question and answer thread…there are other science/archeological topics in this forum go read em
was that a SCIENTIFIC event???
sorry, i thought you were asking people if they any questions regarding science and stuff.
and u still haven’t told me how you figured out the concentration ratio of those firms
http://www3.pak.org/gupshup/smilies/tongue.gif
[This message has been edited by Farwa (edited November 30, 2001).]
Thap don't tell Farwa anything coz she's asking for KasoTi game that is going on in Cafe.
Too bad he already told me
Didn’t know I was involved in espionage
c
Thap....stop making noise about the forum and start talking science. Unfortunately we have to justify the forum's need first.
http://www.sciencenews.org/20011201/fob1.asp
Craft Probes Alien Planet’s Atmosphere
Astronomers have long wondered what the atmospheres of planets beyond the solar system might be like. Researchers this week reported that they have now gotten their first whiff.
The new observations, the researchers say, demonstrate that telescopes will ultimately have the capability to measure the composition of a variety of extrasolar planets’ atmospheres and search for chemical markers of life beyond Earth.
“This is a huge step forward in extrasolar-planet research and one of the biggest discoveries ever in planetary science,” comments theorist Sara Seager of the Institute for Advanced Study in Princeton, N.J. “For the first time, we can start to understand what the atmospheres [of extrasolar planets] are made of.”
In the new study, astronomers homed in on a hot, gaseous planet. It’s about two-thirds as heavy as Jupiter and orbits the sunlike star HD 209458, located 150 light-years from Earth. Researchers were able to detect the atmosphere of the distant planet because it periodically passes directly between its parent star and Earth. During those times, light from the star travels through layers of the planet’s outer atmosphere, so less light reaches Earth.
Using the Hubble Space Telescope, astronomers found that whenever the unseen planet crossed in front of the star, they detected a slight decrease in starlight of a particular wavelength. That wavelength corresponds to the radiation absorbed by sodium atoms, which the researchers therefore say must be present in the planet’s atmosphere.
The technique “is like looking at a very bright search light through a dense fog,” explains Seager. “If some [wavelengths of the light] get more dimmed than others . . . we can tell what the fog is made of.”
David Charbonneau of the California Institute of Technology in Pasadena and Timothy M. Brown of the National Center for Atmospheric Research in Boulder, Colo., announced the findings on Nov. 27 in Washington, D.C. Their team will report the study in the Astrophysical Journal.
Charbonneau and his colleagues got their first inkling that they could study the planet’s atmosphere in 1999, shortly after two other teams independently discovered the orbiting body. The two teams discerned the unseen planet by detecting the slight wobble it induces in the motion of its parent star. Residing much closer to the star than the distance at which Mercury orbits the sun, the planet whips around HD 209458 in just 3.52 days.
Soon after that discovery, Charbonneau, Brown, and another group of astronomers examined the star to see if its planet would periodically block some of the starlight. An observer can see that dip in brightness only if the plane in which the planet orbits is aligned edge on with respect to Earth. The body circling HD 209458 is the only known extrasolar planet to have that alignment. The dimming that researchers detected revealed the planet’s mass and radius (SN: 11/20/99, p. 324: http://www.sciencenews.org/sn_arc99/11_20_99/fob1.htm)..)
The alignment, combined with the planet’s proximity to its parent star, offered “a fantastic opportunity to learn about the planet’s atmosphere,” Charbonneau says.
The intense heat from HD 209458 keeps the planet’s atmosphere inflated like a hot-air balloon. Seager and other researchers calculated that the atmosphere is tenuous enough that each time the planet passes in front of the star, some starlight filters through the atmosphere’s outer layers rather than being blocked altogether.
Models suggest that planetary atmospheres contain only trace amounts of sodium. Nonetheless, Charbonneau’s team searched for this element because even small amounts would absorb enough light to be detected by Hubble’s spectrometer.
Hubble did detect a few parts per million of sodium, but that’s considerably less than any of the models predicted. The atmosphere may simply contain less sodium than expected, notes Seager. Another explanation is that the alien planet’s atmosphere contains dense, high-altitude clouds. These clouds would prevent starlight from penetrating deep into the atmosphere, where much of the sodium may lie.
Charbonneau, Brown, and their colleagues now plan to search for methane, water vapor, potassium, and other chemicals in the atmosphere.
The scorchingly hot planet circling HD 209458 isn’t likely to support life. But astronomers can apply the same search technique to probe the atmospheres of cooler, more hospitable extrasolar planets. The atmospheres of these planets may contain oxygen and other chemicals produced by organisms, Charbonneau notes.
He emphasizes, however, that this method of studying planetary atmospheres works only if a planet passes directly in front of its star as seen from Earth. So-called hot Jupiters, such as the planet closely orbiting HD 209458, have about a 1 in 10 chance of having that alignment. The odds are much less for a planet that lies farther from its star because its orbit must be much more precisely aligned if starlight passing through the atmosphere is to reach Earth.
A network of telescopes that Charbonneau and his colleagues have just begun to use has the potential to find one correctly positioned planet each month, he estimates.
The group recently employed another method to study the atmosphere of the planet circling HD 209458. This time, the researchers used Hubble to measure the intensity of starlight reflected by the planet, rather than the amount transmitted through its atmosphere. The team is now analyzing the data to find variations in the intensity of the reflected light at several wavelengths. The observations may reveal the size of clouds and particles in the atmosphere, Charbonneau says.
http://www.newscientist.com/news/news.jsp?id=ns99991631
Predators key to forest survival
Greg Miller
A forest without predators may not be a forest for long - that is the ominous conclusion of a unique new study by an international team of scientists. The team has found that when predators vanish, herbivore populations can explode, leading to the mass destruction of plant life.
The team, led by John Terborgh of Duke University, conducted a census of the herbivores and trees on several islands in Lago Guri, a 4300 square kilometre lake in Venezuela that was created in 1986 when a river was dammed for hydroelectric power.
When the water rose, the smallest of the islands lost nearly all of the predatory animals that inhabit the mainland, such as jaguars, snakes and raptors. The situation provided a unique natural experiment to test two competing theories of how ecosystems are structured.
The so-called bottom-up theory, says, in effect, that the plants are in control. Proponents of this idea argue that the availability of edible plants determines how many herbivores an ecosystem can support, which in turn determines how many predators it can support.
The top-down theory, on the other hand, argues that the predators are in charge. They keep the herbivores in check, thereby determining the abundance of plants.
Population explosion
“Some theoretical ecologists have argued that these top-down effects aren’t very important or very common,” says Michael Pace of the Institute of Ecosystem Studies in Millbrook, New York. “But these kinds of observations are very hard to make in terrestrial ecosystems, which is why it’s been so hard to tell.”
Until now. The bottom-up theory predicts nothing much should have changed in the Lago Guri after the predators disappeared. But Terborgh’s findings show that the absence of predators has had a profound effect on the islands’ ecosystems.
His team found that herbivores such as howler monkeys, iguanas and leaf-cutter ants were 10 to 100 times more prevalent on the lake’s six smallest islands than they were on the mainland. The density of young trees on these islands was less than half that on six larger islands in the lakes, which had retained some of their predators.
Back lash
Pace says the study illustrates nicely that top-down processes can shape ecosystems, at least in some situations. However, he adds that the pendulum could swing back to bottom-up forces if the herbivores gobble up all the edible plants on the islands. If that happens, the remaining plants could begin limiting animal populations.
The study’s authors argue that predators play a key role in maintaining biodiversity. An overabundance of herbivores “threatens to reduce species-rich forests to an odd collection of herbivore-resistant plants,” they write. “Along the way, much plant and animal diversity will probably be lost.”
This process is already happening in North America, they say, where deer populations have ballooned, and in Malaysia, where wild pigs run rampant through some forests.
http://www.newscientist.com/news/news.jsp?id=ns99991627
**Scientists raise spectre of gene-modified athletes **
James Randerson
Gene doping, in which athletes could genetically modify themselves with performance enhancing DNA, will be almost impossible to detect according to Peter Schjerling at the Copenhagen Muscle Research Centre in Denmark.
And far-fetched as it may seem, we may be watching genetically-modified (GM) athletes as soon as the Beijing Olympics in 2008, according to Charles Yesalis, an expert in performance enhancing drugs at Pennsylvania State University. The predictions are being presented at the Genes in Sport Conference at University College London on Friday.
Schjerling believes cheats will avoid detection by injecting themselves with copies of genes naturally present in the body, such as those encoding growth factors or testosterone.
With so much at stake in competitions, athletes may be prepared to risk therapies that have not been fully tested, says Schjerling: “Gene doping may be available to athletes even faster than normal patients.”
Blood booster
One possibility would be to inject the gene for erythropoietin (EPO), a protein that boosts red blood cell count. This allows an athlete’s blood to carry more oxygen.
In 1998, a whole cycling team was thrown out of the Tour de France for using EPO. But while it is possible to spot the synthetic protein currently used by its molecular differences, EPO from introduced genes would be identical to natural EPO.
Another possible therapy that could be hijacked by the gene cheats is vascular endothelial growth factor (VEGF). Sanjay Rajagopalan and colleagues at the University of Michigan have used a GM virus to deliver the VEGF gene to patients with peripheral atherosclerotic disease. This painful disease results in the constriction of blood vessels to the limbs and can result in patients losing a limb.
The therapy boosts VEGF levels which widens blood vessels. But athletes could use the therapy to increase the blood supply to their muscles, in order to enhance performance.
This gene therapy technique employs the common cold virus to deliver the VEGF gene to cells, so even detecting the virus would not prove an athlete had been cheating.
Biological battle
Detection might be possible if an inserted gene was attached to a distinctive promoter - the genetic sequence that controls a gene’s activity. However, the gene’s uptake would be quite local, so to detect it you would have to take a muscle biopsy from the exact site of an injection - painful procedure with minimal chance of success.
Yesalis is extremely pessimistic about the International Olympic Committee’s ability to keep tabs on the cheats. “There is a gross epidemic of drug use in sport at the moment, so why should I expect any great success against gene therapy” he says.
“Currently the battle is over who has the best chemists, in the future it will be who has the best gene therapists,” he adds.
http://www.newscientist.com/news/news.jsp?id=ns99991610
Flesh-eating bugs become cancer killers
Philip Cohen, San Francisco
Injecting flesh-eating bugs into people with cancer may sound crazy - but initial studies suggest the only danger is that they destroy tumours so fast that the body might not be able to cope with the remains.
The trick is to pick anaerobic bacteria that thrive in the oxygen-poor interior of fast-growing tumours, but die as they reach oxygen-rich healthy tissue.
“The exciting thing is we can combine this approach with chemotherapy and hit the tumour from both the inside and the outside,” says Bert Vogelstein of Johns Hopkins School of Medicine in Baltimore, Maryland.
Tumours supply themselves with food and oxygen by growing blood vessels. But some tumours grow so rapidly their interiors become starved of blood and oxygen, and turn into “necrotic” regions full of dead and dying cells.
Surprisingly, this makes them more difficult to destroy. Drugs cannot reach the tissue at lethal doses because its blood supply is so poor, while radiation treatments depend on oxygen to trigger cell death. After treatment stops, surviving cells from the necrotic region can start dividing again.
All consuming
Cancer researchers have long realised that anaerobic bacteria could be used to attack the necrotic region without harming healthy tissue. But the microbes tested so far have left parts of tumours untouched. So Vogelstein’s team widened the search, testing 26 strains of anaerobic bacteria.
When they injected the soil bacterium Clostridium[ck] novyi into the bloodstream of mice with tumours, it spread throughout the necrotic region, consuming living tumour cells as well as dead tissue.
“That was completely unexpected,” says Vogelstein. “We thought we’d have to genetically engineer it to do that.” However, the microbes perished near the edges of the tumour, leaving the job half done.
So the researchers tried combining the bugs with chemotherapy. “The tumour died so quickly, you could almost watch it,” says Vogelstein. Out of eight animals given the combination treatment, the tumours shrank dramatically or disappeared completely in seven, and regrew only in one, the team reports in the Proceedings of the National Academy of Sciences.
“Combining these different approaches is a very clever move,” says Rakesh Jain, a cancer researcher at Harvard Medical School in Boston. “It’s wonderful work.”
Global supply
The catch is that three of the eight mice died. But the researchers think this could be because the tumours were destroyed so quickly that the waste products flooded the animals’ circulation.
In small animals these toxins spread too quickly to combat, but in humans they should not be lethal. “We’ll need to go to larger animals to test that theory out,” says Vogelstein.
He says it will probably be years before the therapy is ready for its clinical debut. But when the time comes, it will not be hard to stock up on the prolific microbe. “We can grow a world supply of it in my lab in one day,” he says.
http://www.newscientist.com/news/news.jsp?id=ns99991618
Nanotubes hint at room temperature superconductivity
Adrian Cho
Tiny tubes of carbon may conduct electricity without any resistance, at temperatures stretching up past the boiling point of water. The tubes would be the first superconductors to work at room temperature.
Guo-meng Zhao and Yong Sheng Wang of the University of Houston in Texas found subtle signs of superconductivity. It wasn’t zero resistance, but it’s the closest anyone’s got so far. “I think all the experimental results are consistent with superconductivity,” Zhao says. “But I cannot rule out other explanations.”
At the moment no superconductor will work above about 130 kelvin (-143°C). But if a material could carry current with no resistance at room temperature, no energy would be lost as heat, meaning faster, lower-power electronics. And electricity could be carried long distances with 100 per cent efficiency.
Nanotube bundles
Zhao and Wang studied the effects of magnetic fields on hollow fibres of carbon known as “multiwall carbon nanotubes”. Each nanotube is typically a millionth of a metre long, several billionths of a metre in diameter and with walls a few atoms thick. The nanotubes cling together in oblong bundles about a millimetre in length.
The researchers did not see zero resistance in their bundles. They think this is because the connections between the tiny tubes never become superconducting. But they did see more subtle signs of superconductivity within the tubes themselves.
For example, when the researchers put a magnetic field across a bundle at temperatures up to 400 kelvin (127°C), the bundle generated its own weak, opposing magnetic field. Such a reaction can be a sign of superconductivity.
And when the team cooled the bundles from even higher temperatures then turned the external field off, they stayed magnetised. A current running around within the tubes could generate this lingering field if there wasn’t any resistance to make it fade away.
While each effect could have a more prosaic explanation, they varied in similar ways as the temperature of the bundles changed. The correlation suggests superconductivity was responsible, Zhao and Wang argue in a paper to be published in Philosophical Magazine B.
Dominating effect
However, their argument doesn’t convince Paul Grant, a physicist with the Electric Power Research Institute in Palo Alto, California. “Generally, superconductivity is such a dominating effect that when it occurs it just shouts out at you,” Grant says. “It doesn’t appear in these indirect ways.”
Superconductivity theories do not forbid the phenomenon at very high temperatures, says Sasha Alexandrov, a theoretical physicist at Loughborough University in the UK.
A material becomes superconducting when its electrons pair up. Normally such negatively charged particles would repel each other, but in a positively charged crystal structure, vibrations called phonons help them get together. In carbon nanotubes, the frequency of these vibrations is very high, which, in theory at least, means superconductivity at higher temperatures.
“The results on the magnetic response are very intriguing, and favour the explanation they present,” Alexandrov says. “It’s certainly possible,” agrees David Caplin, head of the Centre for High Temperature Superconductivity at Imperial College, London. (<—mAd_ScIeNtIsT’s university)
To decide whether or not the nanotubes really are superconductors, you need to measure the resistance through a single tube, Alexandrov says. “To be convinced, I’d like to see zero resistance.”
http://www.newscientist.com/news/news.jsp?id=ns99991615
Twin gene idea could wipe out malaria mosquito
Every 10 seconds a child dies from malaria - but there may now be a way to control the Anopheles mosquito that spreads the disease.
Scientists say they can genetically modify whole mosquito populations so that the flies are either susceptible to pesticides, or can’t transmit the malaria parasite. And they would only need to release relatively few GM mosquitoes to kick-start the process.
According to the WHO, malaria claims more lives than any other communicable disease except tuberculosis, infecting around 500 million people each year. Yet it’s proved impossible to eradicate the mosquitoes that carry the disease, because the insects are so numerous.
One trick that has worked against the tsetse fly in Zanzibar and the screw worm fly in North America is to release billions of sterilised males to swamp the wild population. Almost all the wild females mate with the sterilised males and the population crashes.
But it’s extremely difficult to rear huge numbers of sterile male Anopheles mosquitoes in captivity as females require constant blood meals to lay eggs, says Chris Curtis at the London School of Hygiene and Tropical Medicine. And anyway, it’s only a short-term solution - even if you could wipe out all the mosquitoes in one area, nearby populations would soon take over.
Jumping genes
Another idea is to modify a population so that it no longer carries the parasite. Two potential methods involve introducing a GM bacterium or harnessing so-called “jumping genes” that occur naturally in fruit flies. But there are fears that the bacteria could spread to other species. And the fruit fly genes won’t spread particularly well through populations of Anopheles.
Now Stephen Davis’s team at the Commonwealth Science and Industry Research Organisation in Canberra, Australia, think they have found a way to safely “infect” whole populations of mosquitoes with detrimental genes.
Davis’s idea is to release engineered males that have two copies of a “type A” gene, and two copies of “type B”. Subsequently, individuals who inherit A and B together will be fine. But those who inherit either A without B or vice versa will die.
Computer models show that modifying just three per cent of the population is enough to spread the genes. “Such a low threshold was a bit of a shock to us,” explains Davis.
Selection pressure
Hybrid offspring from matings between engineered males and wild females are fine because they have one A and one B. But things get interesting when the hybrids start mating. While all the offspring from hybrid/engineered crosses are fine, some of the offspring from the hybrid/wild crosses die because they have an A or a B in isolation.
This creates a selection pressure which drives the genes through the population, as the offspring of wild flies die more often than those of engineered or hybrid flies.
You could exploit this “drive mechanism” to tackle malaria. Other genes, that either kill the malaria parasite or make the flies susceptible to insecticides, can be tagged onto the modified genes, and will also spread through the population.
While no one has tried this out on real flies, Davis thinks it could be the first practical way to modify a whole population.
Thought that Thap may need a bit of a hand getting started here…
http://www.pnl.gov/energyscience/10-01/brf.htm#brf5
World’s Smallest Laser
A research team from the University of California/Berkeley and Lawrence Berkeley National Laboratory has grown the world’s smallest laser—a nanowire nanolaser one thousand times thinner than a human hair.
The laser, one of the first devices to arise from the field of nanotechnology, emits ultraviolet light, but can be tuned from blue to deep ultraviolet. The team grew the lasers using a standard technique called epitaxy, employed broadly today in the semiconductor industry, to grow extremely pure zinc oxide wires only 20 to 150 nanometers in diameter and 10,000 nanometers long (one nanometer is about the size of 10 hydrogen atoms laid side-by-side).
Although the present devices use another laser to excite the zinc oxide molecules, which then emit UV light—a process called optical pumping—the ultimate goal is to “pump” the zinc oxide with electrons so the nanolasers can be integrated into electronic circuits. Once configured to work with electron pumping, the nanolaser could be put to any number of uses. For example, “lab-on-a-chip” devices could contain small laser analysis kits—nanodetectors—with capabilities such as Raman spectroscopy. Alternatively, a solid-state, short-wavelength, ultraviolet laser would allow an increase in the amount of data that can be stored on a high-density optical disk.